1. Field of the Invention
The present invention relates to a catalytic apparatus for a vehicle that is coated with a precious metal and purifies exhaust gas.
2. Description of Related Art
With the increases of use of vehicles and the traffic volume, air pollution due to exhaust gas is on the rise as a serious social problem and the governments of the world has established discharge standards of pollutants in exhaust gas, such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) to regulate the exhaust gas and these regulations are gradually enforced.
Precious metal catalytic apparatus are used in vehicles to satisfy the discharge standards of exhaust gas and a catalytic apparatus of the related art is shown in FIGS. 1 and 2.
A catalytic apparatus 10 of the related art, as shown in the figures, includes a caning 11 where an upper shell 11a and a lower shell 11b are welded, a lower shell cover 12 that is welded to the outer surface of lower shell 11b, a front flange 13 and a rear flange 14 that is integrally connected to the front and rear ends of caning 11 and connected with a front muffler pipe (not shown) and a rear muffler pipe (not shown), respectively, and front substrate 15 and a rear substrate 16 that are disposed apart from each other in caning 11, and mats 17, 18 that cover front substrate 15 and rear substrate 16, respectively.
Front substrate 15 and rear substrate 16 reduce a great amount of pollutants discharged into the atmosphere by accelerating dissolution of hydrocarbon, oxidation of carbon monoxide, and reduction of nitrogen oxide contained in exhaust gas.
A sensor hole 19 is formed through caning 11 to attach a rear oxygen sensor (not shown) and, sensor hole 19 is formed at lower shell 11b. 
However, catalytic apparatus 10 having the above configuration in the related art has a problem in that the number of parts and the cost increase because caning 11 is composed of upper shell 11a and lower shell 11b. 
Further, catalytic apparatus 10 of the related art is assembled by disposing front substrate 15 and rear substrate 16 into lower shell 11b, disposing upper shell 11a on lower shell 11b, and then combining upper shell 11a with lower shell 11b by welding the flange that is the joint of them. However, there is a problem in that it is substantially impossible to weld the entire joint of upper shell 11a and lower shell 11b at uniform pressure, such that non-uniform surface pressure is applied to front substrate 15 and rear substrate 16 and the performance of front substrate 15 and rear substrate 16 is decreased.
Further, catalytic apparatus 10 of the related art has a problem in that it is difficult to change the mold because the cost for manufacturing the mold increases when it is required to change the position of sensor hole 19 from upper shell 11a to lower shell 11b or from lower shell 11b to upper shell 11a. 
Further, referring to the cross section of front flange 13 shown in FIG. 2, in catalytic apparatus 10 of the related art, since the bottom 13a is horizontally formed in the longitudinal direction of caning 11 at a predetermined position from the center of front substrate 15, there is a problem in that exhaust gas flowing inside through front flange 13 cannot pass through the center of front substrate 15 and the performance of purifying toxic substances of front substrate 15 is reduced.
Further, there is a problem in that since the diameter D1 of an inlet 13b and the diameter D2 of an outlet 13c of front flange 13 are the same, exhaust gas flowing inside through front flange 13 passes through front substrate 15 at a high velocity and accordingly front substrate 15 cannot sufficiently purify the toxic substances.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.